Study of total fructan and fructooligosaccharide content in different onion tissues

The objective of this work was to determine the fructan and fructooligosaccharide (FOS) content of different onion tissues in order to evaluate the potential use of onion by‐products from the food industry as a source of FOS and fructans. Assays with two methods were carried out to optimise the extraction procedure. The main FOS, namely kestose (GF₂), nystose (GF₃) and fructofuranosylnystose (GF₄), were measured directly using standard sugars. The method for total fructans was based on enzymatic treatment (Novozym 230) of ethanolic/aqueous extract followed by determination of released fructose and glucose by HPLC. Data showed a clear predominance of GF₂ in every onion tissue and no occurrence of highly polymerised fructans. The tissues richest in fructans were the fleshy layers, so that the outer two fleshy layers turn out to be the best onion by‐product as a possible fructan source. © 2000 Society of Chemical Industry     

Analysis of the Major Flavonol Glycosides Present in Four Varieties of Onion (Allium cepa) and Changes in Composition Resulting from Autolysis

The major flavonoids of mature onion bulb were confirmed as the 3,4′-O-diglucoside (Qdg) and 4′-O-monoglucoside (Qmg) of quercetin using a combination of chromatographic comparisons, mass spectrometry and nuclear magnetic resonance spectroscopy. These two components account for over 85% of the total flavonoids in three varieties of onion with Qdg as the main component. Quercetin is detected in these long stored onions but only at low levels of less than 2% of the total. The remaining flavonoid fraction (approx 15%) comprises upto 17 different components of which quercetin-3-O-glucoside and isorhamnetin glucoside are prominent members although each contribute less than 1% of the total flavonoid fraction. There are significant differences in the levels of Qdg and Qmg between the four different onion varieties analysed; Qdg varying from 50–1300 mg kg^-1 fresh onion tissue and Qmg from 36–394 mg kg^-1. Maceration of the tissue for the three varieties tested led to a loss of Qdg and the appearance of Qmg and free quercetin. In the variety Rijnsburger 50% of the Qdg was degraded in 5 h and had completely disappeared after 24 h. These changes in Qdg can be quantitatively explained by increases in Qmg and free quercetin. The possible significance of quercetin glycosides in the diet is discussed. © 1997 SCI     

Traditional and modern uses of onion bulb (Allium cepa L.): a systematic review

Abstract

Onion, (Allium cepa L.), is one of the most consumed and grown vegetable crops in the world. Onion bulb, with its characteristic flavor, is the third most essential horticultural spice with a substantial commercial value. Apart from its culinary virtues, A. cepa is also used traditionally for its medicinal virtues in a plethora of indigenous cultures. Several publications have been produced in an endeavor to validate such traditional claims. Nonetheless, there is still a dearth of up-to-date, detailed compilation, and critical analysis of the traditional and ethnopharmacological propensities of A. cepa. The present review, therefore, aims to systematically review published literature on the traditional uses, pharmacological properties, and phytochemical composition of A. cepa. A. cepa was found to possess a panoply of bioactive compounds and numerous pharmacological properties, including antimicrobial, antioxidant, analgesic, anti-inflammatory, anti-diabetic, hypolipidemic, anti-hypertensive, and immunoprotective effects. Although a large number of in vitro and in vivo studies have been conducted, several limitations and research gaps have been identified which need to be addressed in future studies.     

Osmotic potential and soluble solids concentration in onion (Allium cepa) bulbs

Non-structural carbohydrate composition of onion (Allium cepa L) bulbs is known to vary between varieties according to soluble solids concentration (SS), which may reduce the effect of SS on osmotic potential. This was confirmed in an experiment where osmotic potential (Ψ_π) was determined psychometrically, and SS concentration refractometrically, in juice from entire, mature bulbs of 35 varieties of onion. ‘Fresh market’ varieties ranged in mean SS from 63 to 125 g kg- and in mean Ψ_π from ?0.97 MPa to ?1.17MPa, whereas ‘dehydrating’ varieties ranged in mean SS from 167 to 227 g kg-¹ and in mean Ψ_π from ?1.23 MPa to ?1.41 MPa. Compared to sugar solutions of constant composition, with increasing SS, there was a relatively slow decline in Ψ_π toward a lower limit at the SS levels of dehydrating varieties. The relationship between Ψ_π and SS was explained equally well (r² = 0.83; DF = 172) by non-linear and bent-stick regression models, the latter indicating breakpoints close to the SS level separating fresh market variety samples from those of dehydrating varieties. Variety differences in the relationship between Ψ_π and SS indicated among dehydrating varieties in particular are worthy of further investigation because of their possible physiological and quality implications.     

Long-term storage of onion and the factors that affect its quality: A critical review

Storage of onions is a multifaceted issue, which involves many preharvest and postharvest factors. One of the major factors that affect onion storage is the selection of the proper cultivar, since there are significant differences in storability between the cultivars and not all of them are suitable for storage. Proper preharvest and postharvest conditions are essential for storability of onion bulbs, whereas they also affect marketability (weight losses, texture and color depth of bulbs) and quality (chemical composition, nutritional value, antioxidant activity). Irrigation and fertilization are essential preharvest factors that substantially affect storability, whereas curing methods and storage conditions (temperature, relative humidity, controlled atmospheres) and processing treatments are postharvest factors. This review article examines the effect of long-term storage on the main quality features of onions, such as the incidence of sprouting and root growth, water losses, and changes in chemical composition (mineral composition, sugar content, nutritional value) and antioxidant activity (phenolic and flavonoid contents, DPPH [2,2-diphenyl-1-picrylhydrazyl] scavenging activity).     

洋葱皮总黄酮的超声波提取工艺研究

以洋葱皮为原料,利用超声波强化提取黄酮类化合物。在单因素试验的基础上,采用正交试验法,考察了乙醇浓度、料液比、超声温度、超声时间和提取次数对总黄酮提取率的影响,并用分光光度标准曲线法测定其含量,最终确定最佳工艺条件为:乙醇浓度为70%、料液比1∶20、超声温度30℃、超声时间15 min。在上述最佳条件下,总黄酮的提取率可达4.412%。     

三种洋葱籽脂肪酸成分的对比研究

采用索氏提取法提取洋葱籽油脂肪酸,提取出的脂肪酸经甲酯化处理后用GC/MS法分析和鉴定其组成。三种洋葱籽油中共分离鉴定出23种脂肪酸,主要成分均为亚油酸、油酸和十六烷酸等,其中不饱和脂肪酸占总量的81.35%(白皮)、82.8%(红皮)和78.94%(黄皮)。结果表明,洋葱籽中不饱和脂肪酸含量丰富,且亚油酸含量很高,将其开发成为药食两用功能性调味品,当具有良好应用前景。